Carrière Yves, Ellers-Kirk Christa, Biggs Robert W, Nyboer Megan E, Unnithan Gopalan C, Dennehy Timothy J, Tabashnik Bruce E
Department of Entomology, 410 Forbes Building, P.O. Box 210036, Tucson, AZ 85721-0036, USA.
J Econ Entomol. 2006 Dec;99(6):1925-35. doi: 10.1603/0022-0493-99.6.1925.
Recessive resistance to Bacillus thuringiensis (Bt) cotton, Gossypium hirsutum L., in laboratory-selected strains of pink bollworm, Pectinophora gossypiella (Saunders), is associated with three resistance alleles (r1, r2, and r3) of a cadherin gene. Previous experiments based on measurement of fitness components in Bt-resistant and Bt-susceptible strains revealed that fitness costs and incomplete resistance are associated with resistance. Here, we used two hybrid strains of pink bollworm, each containing a mixture of susceptible and resistant individuals, and polymerase chain reaction (PCR) amplifications to test the association between cadherin genotype and fitness components for individuals sharing a common genetic background. All survivors on Bt cotton had two r alleles, confirming that recessive cadherin alleles are tightly linked with resistance to Bt cotton. On non-Bt cotton, significantly greater developmental time for rr than ss larvae indicated a recessive fitness cost, but costs did not affect survival or pupal weight. Incomplete resistance was manifested as longer developmental time, lower survival, and smaller pupal weight in rr individuals developing on Bt cotton compared with non-Bt cotton. As in previous experiments, no significant variation in performance on Bt cotton was detected among rr genotypes. However, a meta-analysis of data from seven experiments revealed that survival on Bt cotton relative to non-Bt cotton was lower in r2r3 and higher in r1r2 compared with the other rr genotypes. Assessment of fitness components associated with cadherin genotypes in hybrid strains of pink bollworm confirms that recessive resistance to Bt cotton is associated with recessive fitness costs and incomplete resistance.
在实验室选育的棉铃虫（Pectinophora gossypiella (Saunders)）品系中，陆地棉（Gossypium hirsutum L.）对苏云金芽孢杆菌（Bt）棉花的隐性抗性与钙黏蛋白基因的三个抗性等位基因（r1、r2和r3）相关。先前基于对Bt抗性和Bt敏感品系适合度成分测量的实验表明，适合度代价和不完全抗性与抗性相关。在此，我们使用了两个棉铃虫杂交品系，每个品系都包含易感和抗性个体的混合物，并通过聚合酶链反应（PCR）扩增来测试具有共同遗传背景的个体的钙黏蛋白基因型与适合度成分之间的关联。在Bt棉花上的所有存活个体都有两个r等位基因，证实隐性钙黏蛋白等位基因与对Bt棉花的抗性紧密相关。在非Bt棉花上，rr幼虫的发育时间明显长于ss幼虫，表明存在隐性适合度代价，但这种代价不影响存活或蛹重。不完全抗性表现为与非Bt棉花相比，在Bt棉花上发育的rr个体发育时间更长、存活率更低且蛹重更小。与先前的实验一样，在Bt棉花上的表现，rr基因型之间未检测到显著差异。然而，对七个实验数据的荟萃分析表明，与其他rr基因型相比，r2r3在Bt棉花上的存活率相对于非Bt棉花较低，而r1r2则较高。对棉铃虫杂交品系中与钙黏蛋白基因型相关的适合度成分的评估证实，对Bt棉花的隐性抗性与隐性适合度代价和不完全抗性相关。
